With respect to a process for producing a liquid crystal element, several techniques have heretofore been known.
For example, JP-A-2005-353207 (Patent Document 1) discloses a process for producing a polarized hologram element, characterized by polymerizing the following polymer crystals in such a state that they are aligned in one direction. That is, disclosed are a polarized hologram element comprising a first transparent substrate made of a resin and provided with concavoconvex lattice on one surface, a first transparent conductive film formed on the concavoconvex lattice of the first transparent substrate, a first insulating film covering the first transparent conductive film, a second transparent substrate opposed to the first transparent substrate, a second transparent conductive film formed on the surface on the first transparent substrate side of the second transparent substrate, a second insulating film covering the second transparent conductive film, and a liquid crystal layer filled between the first and second insulating films and containing at least polymer liquid crystals aligned in one direction, and a process for producing such a polarized hologram element, which comprises sandwiching non-cured ultraviolet curable polymer crystals between the first and second insulating films, and applying a voltage to the first and second conductive films to align the polymer crystals in one direction, followed by exposure.
However, in the process for producing a polarized hologram element disclosed in Patent Document 1, it is necessary to carry out exposure after sandwiching non-cured ultraviolet curable polymer crystals between the first and second insulating films and applying a voltage to the first and second transparent conductive films to align the polymer crystals in one direction.
Further, a process is known to form a lattice-form concavoconvex structure in a layer of polymer liquid crystal by dry etching a layer of polymer liquid crystal having alignment controlled in a substrate having a liquid crystal alignment property.
In such a process, polymer liquid crystal molecules may be cleaved by dry etching to generate radicals, whereby the light resistance of the layer of polymer liquid crystal may be deteriorated. Further, it is difficult to improve the precision of the shape of the concavoconvex structure formed by dry etching. Further, although it may be possible to form a concavoconvex structure of a micron size, it is difficult to form a concavoconvex structure of a nanometer size.
Further, for example, a process is known to form a lattice-form concavoconvex pattern in a layer of polymer liquid crystal obtained by polymerizing low molecular weight liquid crystal i.e. by polymerizing (curing) photocurable low molecular weight liquid crystal, while pressing a mold having a reverse pattern of the lattice-form concavoconvex pattern, against a layer of the photocurable low molecular weight liquid crystal (liquid crystal monomer) having alignment controlled in a substrate having a liquid crystal alignment property.
By such a process, it may be possible to form a layer of polymer liquid crystal having better light resistance and better precision of the shape, but due to the alignment-controlling force (anchoring force) of the mold, the alignment direction of the photocurable low molecular weight liquid crystal is disturbed. Therefore, it is difficult to adjust the alignment direction of mesogen groups of the obtainable polymer liquid crystal to the direction of the lattice. Further, although it may be possible to control the alignment of photocurable low molecular weight liquid crystal in a concavoconvex pattern of a nanometer size by the alignment-controlling force of the mold, it may be difficult to control the alignment of photocurable low molecular weight liquid crystal in a concavoconvex pattern of a micron size.
Further, Non-Patent Document 1 discloses the following observation.
That is, with photoreactive polymer liquid crystal, it is possible to control the alignment by irradiation with polarized UV light, and it is possible to control the alignment by a mold pattern by applying thermal nanoprinting to the photoreactive polymer liquid crystal. Firstly, the photoreactive polymer liquid crystal is applied to a glass substrate by spin coating, followed by thermal nanoprinting. At that time, as the mold, a SiO2/Si mold was used, and as a mold release agent, OPTOOL DSX (manufactured by DAIKIN INDUSTRIES, LTD.) was used. The thermal nanoprinting was carried out under a pressure of 20 MPa for a retention time of 1 minute by heating the mold side and the substrate side to 150° C. When the photoreactive polymer liquid crystal is observed by a polarizing microscope, if the alignment is random, the field becomes a dark field, and if aligned in a certain direction, the field becomes a bright field. In a polarizing microscopic photograph of a 2 μm L&S (line and space) imprint pattern on the photoreactive polymer liquid crystal, the L&S pattern portion became a bright field, and a portion having no L&S pattern formed became a dark field. This means that the photoreactive polymer liquid crystal can be aligned by applying thermal nanoprinting to the photoreactive polymer liquid crystal.
However, Non-Patent Document 1 is nothing more than disclosing that thermal nanoprinting was applied to photoreactive polymer liquid crystal having random alignment, whereby the photoreactive polymer liquid crystal was aligned by alignment control by an alignment-controlling force of the mold pattern. That is, there is no disclosure about preventing or reducing disturbance in preliminarily-controlled alignment of photoreactive polymer liquid crystal by a mold, and at the same time imparting an L&S pattern to the photoreactive polymer liquid crystal by pressing a mold against the photoreactive polymer liquid crystal. Further, Non-Patent Document 1 discloses that the mold side and the substrate side are heated to a high temperature of 150° C. in order to control the alignment by a mold pattern.